A molding method using an autoclave has already been established in a case where a CFRP (conductive composite material) is molded by laminating a plurality of prepregs in which conductive fiber woven fabrics, for example, carbon-fiber woven fabrics are impregnated with thermosetting resin. Meanwhile, a molding method, for example, a mold press molding method, alternative to this molding method using an autoclave, is being built recently.
Waviness of carbon fibers that may affect mechanical properties of CFRPs needs to be newly verified for CFRPs molded by a molding method alternative to such a molding method using an autoclave as described above.
For example, assume that a direction along a plane of a test specimen is an in-plane direction and that a laminating direction of prepregs of the test specimen is an out-of-plane direction in a case where the presence or absence of waviness of carbon fibers is examined in the test specimen of CFRP molded into a cuboid by a mold press molding method. Then, in a conventional ultrasonic flaw detection test (see, for example, Patent Document 1), it is possible to detect a condition of carbon fiber waviness in the out-of-plane direction. It is not possible, however, to grasp a condition of carbon fiber waviness in the in-plane direction.
Accordingly, as it stands now, a cutting plane of the CFRP test specimen is observed to verify whether or not fiber waviness is present in this cutting plane or in the vicinity thereof. Alternatively, an X-ray CT inspection is performed on small cut pieces of the CFRP test specimen to examine each cut piece for the presence or absence of waviness of carbon fibers.